Kimball Uprt. rescale

[Richard M]

David and List

	I "rescaled" a Kimball upright from the same era. Mine was a little
taller.  I had the bass strings duplicated by Schaff. On the straight
(unwound) strings I measured the distance and calculated the tension.  I
had just bought an Atari 800 for $1,200  and wanted to get some use from
it.  I had a neat little program in basic set up to do the calculations.
The hardest part was getting the speaking length measurements to 1/8 th of
an inch. (2-3 mm).  However I discovered by entering in variations of an
1/8 inch how much difference this made, not that much.  The idea was to get
a scale uniform in tension.  I had read the book which was a reprint of the
piano maker's conferences of 1915 - 1918, (Piano Tone Building) and was
impressed by the fellow from American Wire and Steel who adovacated an
equal tension scale.  His concern was that wide variations of tension would
result in tuning difficulties and tuning stability problems.  He pointed
out that the tension should never excede the elasticity limit of the wire,
which was considerably under the breaking point of the wire.
	I calculated the existing tensions, then fed in sizes to get a uniform
tension.  In end I opted for a graduated uniform tension scale that went
from 155 lbs in the treble to 180 in the lower tenor.  If I remember, the
original scale of my Kimball also only  used whole sizes of wire.  The
computed scale called for increments of half sizes.  If one note called for
one size string and the next note called for another size, but the two
notes shared a wire, I had to "tie them off".  I can't remember if I had to
drill for new hitch pins, or I chanced two single strings on one hitch pin.
 Probably both. Don't let one of the wires ride too high on the hitch pin.
: (  It was my piano so I felt free to experiment.  I was pleased with the
results.  My only regret is that I did not take pictures, or detailed
notes. Maybe I have the tapes of the computer program some where, but I
don't know if the old Atari will even fire up.
	There used to be a slide rule type string tension calculator.  I saw it in
use and it seems to be simpler than a computer, especially  in the shop.
Now in the APSCO catalogue I see a book of treble string tensions, but I
have not read it.  Maybe some one here can review it?

Richard Moody

	BTW... I "lost" the 1915 Piano Tone Buildng  reprint.  If any one wants to
sell one....


----------
> From: David ilvedson <ilvey@a.crl.com>
> To: pianotech@byu.edu
> Subject: Kimball Uprt.
> Date: Thursday, January 16, 1997 11:04 AM
>
> Dear List,
>
> I have in my shop a 52" Kimball Upright, built in 1903 or so.  I
> have never tried rescaling and wanted input as to the need or
> not.  The scaling as is:
>
> 28 bass unisons
>
> 10 unisons at #19
> 10 unisons at #18
> 12 unisons at #17
>   8 unisons at #16
> 10 unisons at #15
>   6 unisons at #14
>   4 unisons at #13
>
> My question:  Would some 1/2 sizes be useful?  I have never tuned
> this piano but assume it would tune nicely! ?  The area around
> the tuning pins has that Kimball dimpled brass sheet.  Any suggestions
> on a good way to protect it from damage while restringing?
>
> Thanks in advance!
>
> ilvey, RPT
> Pacifica, CA